In Print: Droplets of Rain, Strands of Honey

The Newscripts blog would like to be closer Internet buddies with our glossy print Newscripts column, so here we highlight what’s going on in the current issue of C&EN.
Petrichor: The rainy-day smell comes from a potpourri of compounds. Credit: Shutterstock

Petrichor: The rainy-day smell comes from a potpourri of compounds. Credit: Shutterstock

People living in the Bay Area rarely complain about the weather. But San Francisco-based Senior Editor Jyllian Kemsley tells Newscripts that, lately, she's been a bit wistful for rain. "We’ve had very very little here since December. The California news last week, in fact, was that the water content in the snowpack is 17 percent of 'normal,' " Jyllian says, noting that they probably mean "average" instead of "normal." So for this week's Newscripts print column, Jyllian dug through old literature to learn the chemistry of the scent of rain--or petrichor, as Australian chemists Isabel Joy Bear and R. G. Thomas coined it in 1964. Turns out, they were able to isolate an oily yellow material responsible for the characteristic rain scent (that this Portland-raised Newscripts blogger knows so well). Although Jyllian doesn't know the original motivations of rain-scent researchers, she does point out that Bear appears to have been a talented chemist. Also inspired by a scientific question raised in the 1960s, Jyllian's second Newscripts item discusses why honey and other viscous fluids don't drip off of a spoon like water but instead stretch to lengths that seem to defy physics. Traditionally, scientists thought falling fluid is driven by gravity and not viscosity, but that doesn't explain why honey can maintain a droopy strand for 10 meters or more, whereas a thin stream of water breaks up into droplets after a mere 10 cm.  The '60s scientists weren't the only curiously fascinated ones. Assistant Editor Craig Bettenhausen says: "I distinctly remember when I was a kid turning on the sink, looking at it with a strobe light going, and having my mind blown by the realization that it was lots of little droplets and not a continuous stream." But thanks to a 2013 study, these collective curiosities are answered. The researchers found that the length of a fluid strand depends on small waves in the materials. These waves amplify over time and once large enough, break the fluid stream. Because viscosity dampens the amplification, honey gets to hang on a little big longer.

Author: Sophia Cai

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1 Comment

  1. And lo and behold, perhaps through some Newscripts magic: There is petrichor in Northern California air this afternoon!